1. Field of the Invention
The present invention relates to a hybrid vehicle including a gasoline engine and an electric motor capable of applying an assist force to the gasoline engine.
2. Description of the Related Art
In the control of the gasoline engine, it is conventionally known that when a knocking is generated due to a low octane value of a gasoline, the ignition timing of the gasoline engine is retarded to protect the engine and thereafter, the ignition timing is gradually advanced.
However, if the ignition timing is retarded when the octane value of the gasoline is low, from the viewpoint that the engine is preferentially protected, the output torque from the engine is reduced due to the retarding of the ignition timing and an intrinsic engine output is not obtained when the gasoline is of a low octane value, as compared with the case where the gasoline is of a preset octane value is used, as shown in FIG. 5. Particularly, when a driver unconsciously uses a gasoline of an octane value lower than the preset octane value, the following problem is encountered: the ignition timing remains retarded and the degradation in drivability is generated without the driver being conscious thereof.